Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/01—Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
  • G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
  • G01K7/24—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
  • A61B5/0004—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network characterised by the type of physiological signal transmitted
  • A61B5/0008—Temperature signals
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
  • A61B5/055—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K13/00—Thermometers specially adapted for specific purposes
  • G01K13/20—Clinical contact thermometers for use with humans or animals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
  • G01R33/288—Provisions within MR facilities for enhancing safety during MR, e.g. reduction of the specific absorption rate [SAR], detection of ferromagnetic objects in the scanner room
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R33/00—Arrangements or instruments for measuring magnetic variables
  • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
  • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
  • G01R33/30—Sample handling arrangements, e.g. sample cells, spinning mechanisms
  • G01R33/31—Temperature control thereof
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0271—Thermal or temperature sensors

Definitions

• the following relates generally to a temperature monitoring apparatus and method that can operate in a magnetic resonance (MR) environment. It finds particular application in conjunction with low cost, high resistance non-magnetic printed traces, which operate near a magnetic resonance imaging scanner, and will be described with particular reference thereto. However, it will be understood that it also finds application in other usage scenarios and is not necessarily limited to the aforementioned application.
• MR magnetic resonance
• Temperature monitoring devices need to be used in MR environments to monitor the condition of the patient.
• Current accepted methods include the use of a fiber optic probe.
• a fiber optic cable is connected to the sensing element on the patient, and to the patient monitoring device.
• these fiber optic cables are expensive, can be mechanically delicate, and may suffer from errors as a result of atomic level changes in the sensor material due to strong magnetic fields.
• the use of a standard thermistor in an MR environment would require the use of a distributed or discrete high-resistance cable to connect the sensor to the monitor to overcome the RF heating effects and burn hazards associated with the MR environment.
• These high resistance cables are expensive and do not fully eliminate the burn hazard to patients.
• these cables are difficult to manufacture, are susceptible to triboelectric effects, suffer from inductive pickup, excessive parasitic capacitance, and are hyper sensitive to patient movement.
• ferromagnetic content used in the construction of the temperature-monitoring device may cause the cable to be drawn into the MRI scanner causing damage to the patients, users, or causing the equipment to act as a projectile.
• the radio frequency field produced by the MRI scanner may generate currents in a standard cable using a standard thermistor, or cause "hot-spots" that may increase surface temperatures enough to exceed those allowed by regulatory standards and pose discomfort or a burn hazard to the patient.
• the MRI gradient interference from the MR scanner can also induce currents on standard cables and thermistors and on the connection points producing an additive interference waveform component that potentially gives a false temperature reading.
• the present application discloses a new and improved temperature-monitoring device for use in an MR environment, which addresses the above referred issues, and others.
• a temperature measurement probe for use in a magnetic resonance environment.
• the printed conductor includes an elongated substrate, at least one highly resistance, electrically conductive trace printed on the substrate, and at least one thermistor disposed on the substrate and electrically connected with the trace, the thermistors configured to be placed in thermal communication with a patient in the magnetic resonance environment.
• a magnetic resonance system includes a magnetic resonance scanner and a temperature measurement probe as set forth in the proceeding paragraphs, the temperature measurement probe being disposed in an examination region of the magnetic resonance scanner.
• a method for monitoring patient temperature readings during an MRI includes printing a highly resistive, electrically conductive trace on an elongated substrate and electrically connecting at least one thermistor disposed on the substrate with the trace.
• Another advantage resides in the elimination of ferromagnetic content.
• Another advantage resides in the reduction of patient burn risks.
• Another advantage resides in ability to disinfect the thermistor probe.
• Another advantage resides in improved patient care.
• the invention may take form in various components and arrangements of components, and in various steps and arrangement of steps.
• the drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
• FIGURE 1 diagrammatically shows a magnetic resonance (MR) system with a temperature monitoring apparatus operating inside the MR scanner.
• MR magnetic resonance
• FIGURE 2a is a cross-sectional view diagrammatically showing a substrate with a printed trace with applicable thermistors.
• FIGURE 2b is a side view in partial section diagrammatically showing a temperature sensing thermistor and a reference element on opposite faces of a substrate.
• FIGURE 2c is a top view diagrammatically showing two printed traces with a temperature sensing thermistor and reference element on a common surface of a substrate.
• FIGURE 2d is illustrative of a circuit for converting the thermistor output to temperature.
• FIGURE 3 diagrammatically shows a printed trace and thermistor temperature measurement device in a protective housing or catheter shown in section.
• FIGURE 4 diagrammatically shows a plurality of temperature sensors disposed on a common substrate with tear lines in the elongated substrate that enable placement of the sensors at a plurality of locations.
• FIGURE 5 illustrates a method for monitoring patient temperature readings during a MRI using the printed conductor disclosed herein.
• a magnetic resonance environment includes a magnetic resonance (MR) scanner 100 disposed in a radio frequency isolation room 102 (diagrammatically indicated by a dashed box surrounding the MR scanner 100).
• MR magnetic resonance
• a wire mesh or foil define a Faraday cage or other radio frequency screening structures embedded in or disposed on the walls, ceiling, and floor of the MR room containing the MR scanner 100.
• the MR scanner 100 is shown in diagrammatic side-sectional view in FIGURE 1, and includes a housing 104 containing a main magnet windings 106 (typically superconducting and contained in suitable cryogenic containment, not shown, although a resistive magnet windings are also contemplated) that generate a static (Bo) magnetic field in a bore 108 or other examination region.
• the housing 104 also contains magnetic field gradient coils 120 for superimposing magnetic field gradients on the static (B 0 ) magnetic field.
• Such gradients have numerous applications as is known in the art, such as spatially encoding magnetic resonance, spoiling magnetic resonance, and so forth.
• An imaging subject such as an illustrative patient 122, or an animal (for veterinary imaging applications), or so forth is loaded into the examination region (inside the bore 108 in the illustrative case) via a suitable couch 124 or other patient support/transport apparatus.
• the MR scanner may include numerous additional components known in the art, which are not shown for simplicity, such as magnetic field shims, a whole body radio frequency (RF) coil disposed in the housing 104, and so forth.
• the MR scanner also typically includes numerous auxiliary or ancillary components again not shown for simplicity, such as power supplies for the main magnet 106 and the magnetic field gradient coils 120, local RF coils (e.g.
• MR scanner 100 which is a horizontal bore type scanner, is merely an illustrative example and that more generally the disclosed MR safe cables and electrodes are suitably employed in conjunction with any type of MR scanner (e.g., a vertical bore scanner, open-bore scanner, or so forth).
• the main magnet 106 operates to generate a static B 0 magnetic field in the examination region 108.
• RF pulses are generated by the RF system (including for example a transmitter and one or more RF coils disposed in the bore or a whole-body RF coil in the housing 104) at the Larmor frequency (i.e., magnetic resonance frequency) for the species to be excited (usually protons, although other species may be excited, e.g. in MR spectroscopy or multinuclear MR imaging applications).
• These pulses excite nuclear magnetic resonance (NMR) in the target species (e.g., protons) in the subject 122, which are detected by a suitable RF detection system (e.g., a magnetic resonance coil or coils and suitable receiver electronics).
• NMR nuclear magnetic resonance
• Magnetic field gradients are typically applied by the gradient coils 120 before or during excitation, during a delay period (e.g., time to echo or TE) period prior to readout, and/or during readout in order to spatially encode the NMR signals.
• An image reconstruction processor applies a suitable reconstruction algorithm comporting with the chosen spatial encoding in order to generate a magnetic resonance image, which may then be displayed, rendered, fused or contrasted with other MR images and/or images from other modalities, or otherwise utilized.
• temperature measurements are acquired using a temperature measurement probe 130.
• a printed conductor for temperature measurement probe 130 is displayed on the patient 122 and in connection with a monitor 132 (located outside or optionally inside) the MR chamber 102.
• the temperature-measurement probe 130 may have sufficiently low power consumption that the temperature function may be integrated into a battery powered control and processing circuit 128 that communicates wirelessly 134 (showing as a dashed line from the battery powered control and processing circuit to the monitor) with the monitor 132.
• the temperature measurement probe 130 with a conductive trace printed cable 126 and the battery powered control and processing circuit 128 may record surface or invasive temperature measurements of the patient 122.
• the conductive trace printed cable 126 may further be integrated into other cables particularly for surface use.
• a controlled resistance printed electrical trace or conductive trace, 200 is printed on a flexible, MR neutral substrate 202 to form the planar lead cable 126 between a thermistor 204 on the patient 122 and the sensing monitor 128.
• the substrate 202 may be any flexible magnetic resonance inert planar material such as a polymer resin-based film or Mylar. The substrate 202 material is selected so that Proton emissions do not degrade the MR image.
• the conductive trace 200 is formed of carbon-based ink.
• the conductive trace 200 may optionally be silicon based or may be made from a doped semiconductor material.
• the printed conductive traces 200 and thermistors 204 should be non-ferromagnetic to inhibit distortion of magnetic fields and to inhibit the magnetic field and gradient from adversely affecting the probe.
• the conductive trace 200 is configured to inhibit eddy current from forming in the trace and causing resistive heating.
• the traces can be of high resistance and can include slots or other constructs that inhibit eddy current loops.
• Connection probes are printed or applied at the thermistor end of the trace and a control and processing circuit to facilitate connection to the thermistor 204 and the control and processing circuit 128.
• the conductive printed trace may be solid or may contain features such as cross-hatching to inhibit eddy current generation in the conductive printed trace.
• the cross-hatching 206 in the trace 204 improves functional performance by reducing the induction of interference currents in the electrode and resistive traces from the RF and gradient magnetic fields.
• the thermistor 204 is a high resistance thermistor preferably on the order of 10,000 k Ohms, tuned to respond linearly in the range of human body temperatures with the low cost.
• the printed conductive trace 200 resistance can be in the order of 8-10 k Ohms per foot, which may be achieved by printing with a conductive ink in the order of 10 ohms per square.
• the printed conductive trace resistance can be laser trimmed to achieve a desired target resistance to narrow the traces or by forming eddy current inhibiting longitudinal slots.
• the thermistor 204 may be attached by surface mount leads or attached used conductive leads.
• temperature sensitive thermistor 204 and a reference resistor or thermistor 208 are connected in loops with printed input and output traces 200a, 200b, which are printed on opposite faces of the substrate 202.
• One of the thermistors is applied to the patient and the reference element is thermally isolated from the patient or is selected to have stable resistance across the temperature range of interest.
• the temperature sensing element signal is indicative of temperature with RF field induced currents to and the reference element signal is indicative of RF field induced currents which allow for elimination of RF field induced currents by using a common mode filter.
• the resistance may be evenly or unevenly distributed along the printed conductive cable trace 200. Uneven distribution can be achieved by varying the width and or thickness of the printing pattern. Notch or low pass filed integrated circuit components, antenna circuits, power supplies, sensors (piezo, MEMS, accelerometers) may be optionally incorporated into the printed conductive cable trace 200.
• a circuit is formed by the temperature sensing thermistor 204, and the reference elements 208, e.g. a reference resistor, two input traces 200a, 200b, two return traces 200b, 200b' connected to the two input traces 200a, 200b (connection not shown) disposed on a common face of the substrate 202 and the processing and control circuit 128.
• the reference elements 208 e.g. a reference resistor, two input traces 200a, 200b, two return traces 200b, 200b' connected to the two input traces 200a, 200b (connection not shown) disposed on a common face of the substrate 202 and the processing and control circuit 128.
• the process and controlled circuit 128 translates the currents through or voltages across the thermistors into temperature values for transmission to the monitor 132.
• the circuit includes a battery 250 or other power supply outside of the MR environment.
• a filter 252 corrects for noise in the thermistor signals, e.g., by subtracting the noise signal from the reference element 200 from the noisy temperature signal from the temperature measuring thermistor 204.
• a control or processor 254 converts the temperature into a temperature, e.g. using a look-up table stored in an EPROM 256. The look-up table can further compensate for variations from one temperate sensor to the next.
• An RF transmitter 258 transmits the determined temperature value to an RF receiver connected with the monitor 132. It is to be appreciated that the filtering and the conversion to temperature can, in full or in part, be performed at the monitor 132.
• the printed conductive traces 200 are suitably formed of carbon-based ink with specific electrical resistance applied to the planar flexible substrate with predefined electrical resistance applied to the planar flexible substrate 202 to achieve the desired resistance and thermal characteristics.
• the printed conductive traces 200 may be applied by any reproductive method such as by screen-printing.
• the printed conductive traces 200 may be solid or may contain features such as hatching, longitudinal slots, or the like.
• a protective jacket 300 covers the probe and can provide electrical insulation and protection.
• the protective layer 300 is preferably electrically insulating compared with the material of the printed conductive traces 200, and non- ferromagnetic and MR compatible.
• the protective layer is ideally a material that is low cost and sterilisable.
• the sterilisiable protective jacket allows the probe to be inserted into the patient during an MR to provide internal temperature measurement to further protect from injury to the patient.
• the protective layer 300 can have a foam insulating layer to insulate the circuit from induction of interference currents in the electrode and resistive traces from static and gradient magnetic fields.
• a reference resistor or thermistor 208 may be added to create the common mode signal for subtraction from the patient temperature measuring thermistor 204 to compensate for the common mode.
• the housing 300 can be part of a catheter that is configured for other functions.
• the temperature measurement probe 130 may include a plurality of printed traces on one face of the elongated substrate 202, a plurality of return traces (not shown) on an opposite face, a plurality of thermistors 204a, 204b, 204c, and a plurality of reference elements 208a, 208b, 208c.
• connection pads 220 e.g. silver chloride
• Tear lines 210a, 210b are defined in the elongated substrate 202. The tear lines 210a, 210b in the substrate 202 allow the printed traces 200a, 200b, 200c to be separable to accommodate multi-site sensing on various patient body types.
• the substrate is cut to size and the conductive traces and the connection pads are printed on the substrate.
• the thermistor 204, the reference element 208, and the circuit 128 are connected to the connection pads.
• the temperature of the probe is monitored during operation.
• the printed conductor for temperature measurement probe 130 is attached to the patient 122.
• the printed conductor 126 of temperature measurement probe 130 is connected to a patient monitor 132 either wirelessly 134 or through a wired connection.
• the probe Upon activation of the MR system 100, in a step 402, the probe receives a noise on the printed trace 200 created by the MR system 100.
• the probe 130 preferably contains a reference element 208, e.g.
• a current is sent through the thermistor 204 and the reference element 208.
• the currents flowing through the thermistor 204 and the reference element 208 are determined and compared.
• the current through the thermistor is indicative of the MR induced noise and temperature.
• the current through the reference resistor is indicative of MR induced noise.
• the comparison of the current flowing through the reference element 208 and the thermistor 204 allows the current or signal from the thermistor 204 to be corrected for noise.
• the corrected temperature signal is converted to a temperature, e.g. with a look-up table.
• the temperature is communicated to and displayed on the monitor 132, e.g. by RF transmission lines.

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• Health & Medical Sciences (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Surgery (AREA)
• Veterinary Medicine (AREA)
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• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
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• Molecular Biology (AREA)
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• Animal Behavior & Ethology (AREA)
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• Public Health (AREA)
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• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Computer Networks & Wireless Communication (AREA)
• Nonlinear Science (AREA)
• Physiology (AREA)
• High Energy & Nuclear Physics (AREA)
• Radiology & Medical Imaging (AREA)
• Magnetic Resonance Imaging Apparatus (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)
• Measuring And Recording Apparatus For Diagnosis (AREA)

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• 2015
  • 2015-03-31 CN CN201580020059.XA patent/CN106415225B/zh active Active
  • 2015-03-31 JP JP2016561832A patent/JP6574443B2/ja active Active
  • 2015-03-31 EP EP15718099.3A patent/EP3149507B1/en active Active
  • 2015-03-31 BR BR112016023692A patent/BR112016023692A2/pt not_active Application Discontinuation
  • 2015-03-31 WO PCT/IB2015/052351 patent/WO2015159171A1/en active Application Filing
  • 2015-03-31 RU RU2016144725A patent/RU2678794C2/ru active
  • 2015-03-31 US US15/302,529 patent/US10271736B2/en active Active

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